1 files changed, 61 insertions, 0 deletions

diff --git a/lib/mpi/generic_mpih-mul3.c b/lib/mpi/generic_mpih-mul3.c
new file mode 100644
index 000000000000..f96df327be63
--- /dev/null
+++ b/lib/mpi/generic_mpih-mul3.c
@@ -0,0 +1,61 @@
+/* mpihelp-mul_3.c  -  MPI helper functions
+ * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ *
+ * Note: This code is heavily based on the GNU MP Library.
+ *       Actually it's the same code with only minor changes in the
+ *       way the data is stored; this is to support the abstraction
+ *       of an optional secure memory allocation which may be used
+ *       to avoid revealing of sensitive data due to paging etc.
+ *       The GNU MP Library itself is published under the LGPL;
+ *       however I decided to publish this code under the plain GPL.
+ */
+
+#include "mpi-internal.h"
+#include "longlong.h"
+
+mpi_limb_t
+mpihelp_submul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
+                 mpi_size_t s1_size, mpi_limb_t s2_limb)
+{
+        mpi_limb_t cy_limb;
+        mpi_size_t j;
+        mpi_limb_t prod_high, prod_low;
+        mpi_limb_t x;
+
+        /* The loop counter and index J goes from -SIZE to -1.  This way
+         * the loop becomes faster.  */
+        j = -s1_size;
+        res_ptr -= j;
+        s1_ptr -= j;
+
+        cy_limb = 0;
+        do {
+                umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
+
+                prod_low += cy_limb;
+                cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high;
+
+                x = res_ptr[j];
+                prod_low = x - prod_low;
+                cy_limb += prod_low > x ? 1 : 0;
+                res_ptr[j] = prod_low;
+        } while (++j);
+
+        return cy_limb;
+}